1. Field of the Invention
The invention relates to a commutator for an electrical machine.
2. Description of the Prior Art
One such commutator is already general prior art in a direct current motor, and has laminations disposed on a commutator body that are electrically contacted or connected, on the side toward one winding side of an armature, to the winding ends of the wire windings. As a result of the centrifugal forces engendered by the rotation of the armature, the connections between the wire ends or winding ends and the laminations must be embodied so as to be stable, even at relatively high rotary speeds of the armature.
It is therefore known for the ends, toward the wire windings, of the laminations to be bent over radially outward and back, so that the ends of the laminations point away from the wire windings. This hooklike embodiment of the lamination ends ensures a secure physical contact or in other words fastening of the winding ends on the lamination ends.
It is furthermore known for slots, in which the ends of the wire or winding can be placed, to be embodied on the laminations. By way of the winding ends, fixed in the slots in particular by soldered or welded connections, a secure connection can likewise be achieved. In commutators with slots on the lamination end, the maximum diameter of the winding wires is restricted by the width at the lamination end, or by the diameter of the lamination face. So that the winding wires can be connected securely to the laminations, additional provisions are therefore necessary. In commutators with hooklike lamination ends, and especially with a high number of laminations, the diameter of the commutator body and the disposition of the laminations are critical, in the sense that the ends of adjacent windings must be prevented from touching in the vicinity of the laminations, because that could lead to a short circuit between the affected windings.
One provision for reducing or preventing the problems discussed is to reduce the number of laminations, or to reduce the wire diameter of the windings. Another provision is to increase the diameter of the lamination face or to use a plurality of thinner, parallel-connected wires. However, all of these provisions can lead to unwanted properties of the electrical machine. For instance, the geometric replaceability of rotors or machines from the same series for different operating voltages can prove difficult. It is also conceivable that the service life of the carbon brushes and/or of the commutator will be shortened. Furthermore, heating of the windings, reduced efficiency, or running noise can occur. Because of the relatively high power density, these effects are more highly pronounced in relatively small electrical machines than in larger ones.